The famous orator known for his speeches on liberty and justice was Frederick Douglass. An escaped slave, Douglass became a prominent social reformer and abolitionist in the 19th century. His eloquent speeches, such as "What to the Slave Is the Fourth of July?" powerfully articulated the injustices faced by African Americans and urged for equality and human rights. Douglass' ability to convey the emotional and moral urgency of freedom galvanized public opinion and significantly contributed to the abolitionist movement, making him one of the most impactful voices for social justice in American history.